matplotlib
diff --git a/‎lib/matplotlib/colorbar.py
Lines changed: 17 additions & 8 deletions b/‎lib/matplotlib/colorbar.py
Lines changed: 17 additions & 8 deletions
diff --git a/‎lib/matplotlib/contour.py
Lines changed: 5 additions & 7 deletions b/‎lib/matplotlib/contour.py
Lines changed: 5 additions & 7 deletions
diff --git a/‎lib/matplotlib/tests/baseline_images/test_axes/contour_colorbar.pdf
259 KB b/‎lib/matplotlib/tests/baseline_images/test_axes/contour_colorbar.pdf
259 KB
diff --git a/‎lib/matplotlib/tests/baseline_images/test_axes/contour_colorbar.png
147 KB b/‎lib/matplotlib/tests/baseline_images/test_axes/contour_colorbar.png
147 KB
@@ -255,7 +255,7 @@ def __init__(self, ax, cmap=None,
         self.filled = filled
         self.extendfrac = extendfrac
         self.solids = None
-        self.lines = None
+        self.lines = list()
         self.outline = None
         self.patch = None
         self.dividers = None
@@ -467,14 +467,18 @@ def _add_solids(self, X, Y, C):
                               )
             self.ax.add_collection(self.dividers)
 
-    def add_lines(self, levels, colors, linewidths):
+    def add_lines(self, levels, colors, linewidths, erase=True):
         '''
         Draw lines on the colorbar.
 
         *colors* and *linewidths* must be scalars or
         sequences the same length as *levels*.
+
+        Set *erase* to False to add lines without first
+        removing any previously added lines.
         '''
         y = self._locate(levels)
+        nlevs = len(levels)
         igood = (y < 1.001) & (y > -0.001)
         y = y[igood]
         if cbook.iterable(colors):
@@ -490,9 +494,10 @@ def add_lines(self, levels, colors, linewidths):
             xy = [zip(Y[i], X[i]) for i in xrange(N)]
         col = collections.LineCollection(xy, linewidths=linewidths)
 
-        if self.lines:
-            self.lines.remove()
-        self.lines = col
+        if erase and self.lines:
+            for lc in self.lines.pop():
+                lc.remove()
+        self.lines.append(col)
         col.set_color(colors)
         self.ax.add_collection(col)
 
@@ -843,10 +848,13 @@ def on_mappable_changed(self, mappable):
         self.set_clim(mappable.get_clim())
         self.update_normal(mappable)
 
-    def add_lines(self, CS):
+    def add_lines(self, CS, erase=True):
         '''
         Add the lines from a non-filled
         :class:`~matplotlib.contour.ContourSet` to the colorbar.
+
+        Set *erase* to False if these lines should be added to
+        any pre-existing lines.
         '''
         if not isinstance(CS, contour.ContourSet) or CS.filled:
             raise ValueError('add_lines is only for a ContourSet of lines')
@@ -860,7 +868,8 @@ def add_lines(self, CS):
         #tcolors = [col.get_colors()[0] for col in CS.collections]
         #tlinewidths = [col.get_linewidth()[0] for lw in CS.collections]
         #print 'tlinewidths:', tlinewidths
-        ColorbarBase.add_lines(self, CS.levels, tcolors, tlinewidths)
+        ColorbarBase.add_lines(self, CS.levels, tcolors, tlinewidths,
+                                erase=erase)
 
     def update_normal(self, mappable):
         '''
@@ -893,7 +902,7 @@ def update_bruteforce(self, mappable):
         self.outline = None
         self.patch = None
         self.solids = None
-        self.lines = None
+        self.lines = list()
         self.dividers = None
         self.set_alpha(mappable.get_alpha())
         self.cmap = mappable.cmap
 
@@ -1494,7 +1494,7 @@ def _initialize_x_y(self, z):
             scaling data values to colors. If *norm* is *None* and
             *colors* is *None*, the default linear scaling is used.
 
-          *vmin*/*vmax*: [ *None* | scalar ]
+          *vmin*, *vmax*: [ *None* | scalar ]
             If not *None*, either or both of these values will be
             supplied to the :class:`matplotlib.colors.Normalize`
             instance, overriding the default color scaling based on
@@ -1561,18 +1561,16 @@ def _initialize_x_y(self, z):
             linewidths in the order specified
 
           *linestyles*: [ *None* | 'solid' | 'dashed' | 'dashdot' | 'dotted' ]
-            If *linestyles* is *None*, the 'solid' is used.
+            If *linestyles* is *None*, the default is 'solid' unless
+            the lines are monochrome.  In that case, negative
+            contours will take their linestyle from the ``matplotlibrc``
+            ``contour.negative_linestyle`` setting.
 
             *linestyles* can also be an iterable of the above strings
             specifying a set of linestyles to be used. If this
             iterable is shorter than the number of contour levels
             it will be repeated as necessary.
 
-            If contour is using a monochrome colormap and the contour
-            level is less than 0, then the linestyle specified
-            in ``contour.negative_linestyle`` in ``matplotlibrc``
-            will be used.
-
         contourf-only keyword arguments:
 
           *nchunk*: [ 0 | integer ]